May 19, 2026 04:00 PM
https://www.theclimatebrink.com/p/on-the-death-of-rcp85
INTRO: With the release of the new van Vuuren et al 2026 paper on the emissions scenarios that will be used in the upcoming IPCC 7th Assessment Report, the internet has been abuzz with debate over the implications of the formal retirement of the RCP8.5/SSP5-8.5 scenario. The president of the United States even weighed in over the weekend in his own unique style, posting that “the United Nations TOP Climate Committee just admitted that its own projections (RCP8.5) were WRONG! WRONG! WRONG!”.
van Vuuren et al justify this move by noting that “the CMIP6 high emission levels (quantified by SSP5-8.5) have become implausible, based on trends in the costs of renewables, the emergence of climate policy and recent emission trends,” citing the paper that we published in Nature back in 2020.
Others have pointed out that RCP8.5 was never particularly plausible, and have criticized claims that the move away from using these scenarios reflects actual progress on reducing emissions.
So what actually happened here? It turns out that two things can be true at the same time:
RCP8.5 (and its successor SSP5-8.5) were designed to be a worst case emissions scenario, not the most likely outcome even in a world that did nothing to address climate change. We were probably never headed to a tripling of global emissions by 2100 (to say nothing of a five-fold increase in coal use), even in the absence of climate policy.
Rapid declines in clean energy costs have bent the curve of future emissions downward, with new scenarios designed to reflect current policies notably lower than most baseline scenarios in the literature. The 21st century is now unlikely to see a continued expansion of fossil fuel use globally, with current policy scenarios reflecting relatively flat global emissions going forward.
[...] o if we were likely never heading for a world of RCP8.5, with its tripling of global CO2 emissions by 2100 (and five-fold increase in coal use), where were we actually headed? How much has the energy transition to-date (which has grown to over $2 trillion annual global spending) actually changed our future trajectories?
This is an impossible question to precisely answer given that it relies on an inherently unknowable counterfactual scenario... (MORE - details)
INTRO: With the release of the new van Vuuren et al 2026 paper on the emissions scenarios that will be used in the upcoming IPCC 7th Assessment Report, the internet has been abuzz with debate over the implications of the formal retirement of the RCP8.5/SSP5-8.5 scenario. The president of the United States even weighed in over the weekend in his own unique style, posting that “the United Nations TOP Climate Committee just admitted that its own projections (RCP8.5) were WRONG! WRONG! WRONG!”.
van Vuuren et al justify this move by noting that “the CMIP6 high emission levels (quantified by SSP5-8.5) have become implausible, based on trends in the costs of renewables, the emergence of climate policy and recent emission trends,” citing the paper that we published in Nature back in 2020.
Others have pointed out that RCP8.5 was never particularly plausible, and have criticized claims that the move away from using these scenarios reflects actual progress on reducing emissions.
So what actually happened here? It turns out that two things can be true at the same time:
RCP8.5 (and its successor SSP5-8.5) were designed to be a worst case emissions scenario, not the most likely outcome even in a world that did nothing to address climate change. We were probably never headed to a tripling of global emissions by 2100 (to say nothing of a five-fold increase in coal use), even in the absence of climate policy.
Rapid declines in clean energy costs have bent the curve of future emissions downward, with new scenarios designed to reflect current policies notably lower than most baseline scenarios in the literature. The 21st century is now unlikely to see a continued expansion of fossil fuel use globally, with current policy scenarios reflecting relatively flat global emissions going forward.
[...] o if we were likely never heading for a world of RCP8.5, with its tripling of global CO2 emissions by 2100 (and five-fold increase in coal use), where were we actually headed? How much has the energy transition to-date (which has grown to over $2 trillion annual global spending) actually changed our future trajectories?
This is an impossible question to precisely answer given that it relies on an inherently unknowable counterfactual scenario... (MORE - details)